• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.27-30
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• 2008

Nano-sized phosphor powders were synthesized by the liquid phase method to confirm the size and morphology. By using the process, red phosphor particles with a size of 80 nm were obtained. The characteristic comparison of $Y_2O_3:Eu^{3+}$ and $YBO_3:Eu^{3+}$ was carried out and, as a result, $YBO_3:Eu^{3+}$ powders using boric salt showed an aggregated morphology and lower PL performance compared to $Y_2O_3:Eu^{3+}$.

• Journal of Ocean Engineering and Technology
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• v.24 no.5
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• pp.31-38
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• 2010

The Floating storage and re-gasification unit (FSRU), which has large cargo storage tanks, is a floating liquefied natural gas (LNG) import terminal. The sloshing motion in tanks that are partially filled with LNG can cause impact pressure on the containment system and affect the global motion of the FSRU. Therefore, the accurate prediction of sloshing motion has been a significant issue in the offshore gas production industry. In this paper, a particle method based on the moving particle semi-implicit (MPS) method proposed by Koshizuka and Oka (1996) has been modified to predict sloshing motion accurately in a rectangular tank with the filling ratio of water. The simulation results, including the violent sloshing of the fluid, were validated by comparison with the original MPS method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.167-168
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• 2012

본 연구는 해양퇴적물 준설 중 해양의 탁도와 2차오염을 유발하는 미세한 입자의 퇴적물을 생물학적으로 처리하는 친환경 정화기술로 유용미생물제제(BM-S-1)를 투여한 Lab Scale의 실험장치를 이용하여 기초 실험을 수행하였다. 유용미생물제제(BM-S-1)가 우점되어 있는 Lab Scale 실험장치를 운전하여 유기물 정량분석방법인 COD, T-N, T-P를 분석해본 결과 모든 항목이 약 98% 이상 처리됨을 확인할 수 있었다. 특히 본 실험대상물질인 해양퇴적물은 고농도의 염분이 함유되어 있어 기존기술만으로는 생물학적 처리가 어려웠지만, 본 연구에서 사용된 유용미생물제제(BM-S-1)은 염분이 함유된 오염 퇴적물에서도 효과적인 생물학적 처리가 가능함을 확인 할 수 있었다. 따라서 준설 시 2차오염을 유발시키는 미세한 입자의 해양퇴적물을 본 공법으로 처리하여 방류할 시 친환경적인 준설이 이루어질 수 있으며 이 때 처리되어 배출되는 미세토양은 재이용 가능하다고 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.715-722
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• 2016

Most of the domestic railroad tracks are ballast track and repetitive maintenance is required in this track. Therefore, it is necessary to optimize maintenance process for maintenance cost reduction and more effective maintenance. For this, it is important to develop a reasonable settlement progressive model of ballast layer. However, the behavior of ballast is different to that of soils, since ballast is composed of large coarse gravel. Thus, in this study, we carried out numerical analysis by using the discrete element method (PFC 2D) for better understanding of ballast settlement and development of reasonable settlement progressive model. And, we evaluated the settlement of ballast according to particles shape, porosity and loading conditions.

• The Korean Journal of Mycology
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• v.20 no.2
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• pp.149-153
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• 1992

This study aimed to investigate possible cause of slow and abnormal growth of oyster mushrooms, Pleurotus florida and P. ostreatus collected from bad crop farms. Spherical virus particles of 30 nm in diameter from P. florida, 23 nm particles from P. ostreatus, and both 23 and 30 nm particles were also found from interspecies mated culture between P. florida and P. osreatus. The virus particles might be associated with the bad crop of Pleurotus species.

• Journal of ILASS-Korea
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• v.8 no.1
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• pp.16-22
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• 2003

Zeta potential measurements of colloid particles suspended in a liquid are performed by a Zeta Meter developed. There are many applications of colloid stability in spray technology, paints, wastewater treatment, and pharmaceuticalse. Zeta potentials of charged particles are obtained by measuring the electrophoretic velocities of the particles using video enhanced microscopy and image analysis program. The values of zeta potential of polystyrene latex(PSL), $silica(SiO_2)$M, polyvinylidence difluoride(PVDF), silicon nitride, and alumina particles in deionized (DI) water were measured to be -40.5, -31.9, -25.2, -15.1 and -10.1mV, respectively. The particles having high zeta potential less than -20 mV are stable in DI water, because the double layers of them have strong repulsive forces mutually, and the particles having low zeta potential over -20mV are unstable due to Van Der Waals forces. Silica(>20nm), PSL, aluminum and PVDF particles were found to be stable that would remain separate and well disperse, while silicon nitride and alumina particles were found to be unstable that would gradually agglomerate in DI water.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.38-42
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• 2011

토석류는 산간지역에서 발생할 수 있는 가장 위험한 자연재해 중 하나로 입자-유체 혼합물인 토석류가 중력에 의해 매우 빠른 속도로 이동하는 현상을 의미한다. 산간지역에서의 토석류 발생은 도로의 횡단 배수 구조물의 통수능을 저하시키게 되며 그 결과 도로의 유실 등 막대한 피해를 발생시킨다. 잠재적인 토석류 발생 지역에서의 피해 저감을 위해서는 진보된 설계 기준이 마련되어야 하며 이를 위해 토석류의 횡단 배수구조물 내에서 토석류의 동적 거동 특성을 파악하는 것이 선행되어야 할 것이다. 이번 연구에서는 수리 실험을 통하여 횡단 배수구조물 내에서 토석류의 퇴적 특성을 파악하고자 한다. 수리 실험 장비는 폭이 일정한 사각형 수로로 접근 수로와 하류부 수로로 구성되어 있으며 접근수로의 상단부에서 일정한 유량의 토석류를 연속적으로 유입시켜 경사가 급변하는 하류부 수로 내에서의 토석류 퇴적 특성을 파악하였다. 실험 결과로 토석류의 거동 특성은 토석류의 체적 농도, 입자의 특성, 그리고 접근수로와 하류부 수로의 바닥 경사에 종속됨을 정량적으로 알 수 있었다. 또한, 토석류의 체적 농도나 수로 바닥경사 등과는 상관없이 토석류의 퇴적은 하류부 수로의 종단부인 자유 낙하 지점에서부터 시작되었고 시간이 경과함에 따라 퇴적 지점이 접근 수로 쪽으로 이동하며 퇴적량이 크게 증가하는 현상을 보였다. 이 때, 하류부 수로 내 퇴적된 토석류는 약 $12{\sim}15^{\circ}$의 경사를 보였다.

• Applied Chemistry for Engineering
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• v.20 no.5
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• pp.565-569
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• 2009

Nano-sized green and blue phosphor powders were synthesized by liquid phase method to confirm the size and morphology. By using that process, the particle sizes of green and blue phosphor particles were 80 nm and 60 nm, respectively. The characteristic comparison of $Zn_2SiO_4$ : Mn and BAM : Eu was carried out and as a result, $Zn_2SiO_4$ : Mn powders showed an higher PL performance compared to BAM : Eu.

• The Journal of Engineering Geology
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• v.4 no.2
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• pp.231-243
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• 1994

To better understand the fundamental problems of the true micro-damage in medium-grained granite under uniaxial compressive stress, micro-damage localization, initiation and propagation have been observed in a great detail in contact portion of two grains such as quartz and feldspar. For this purpose, new experimental system allowing us to observe the micro-damaging process continuously was developed. Earlier studies used the specimens of unloaded state and it is difficult to visualize stress-induced microcracks under unloading state. Thus, direct observation under loading state is very important for understanding the true micro-damage process. The results explain well the mechanism of micro-damage at two grains, and mechanics of the micro-damage is clarified well by Hertzian fracture mechanics.

• The Journal of Engineering Geology
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• v.4 no.2
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• pp.139-151
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• 1994

Rocks are composed of the discrete elements of microstructures such as different grains and microcracks. The studies of these microstructures are of increasing interest in engineering geology and civil engineering related to construction of a deep under-ground space. Accordingly, instead of a simplified continuum approach, discrete structural elements and mechanical properties of various grains must be accounted. But it is difficult to analyse crack and discontinuity surfaces in Euclidean geometry. So, Mandelbrot( 1983) developed fractal theory to manage irregular body in nature. In this study, geometrical properties of microstructures to estimate a relation between crack propagation and stress were calculated. Then it is shown that fractal theory can be applied to research real mechanical behavior of rocks.